Cutting tools of the type generally mentioned above are useful in machines for the cutting of tubes of metal by parting and grooving. Such machines include a fixed front frame having a central opening, from the inner edge of which a plurality of tools project pointing toward a center where the tube is located. In the machine, a rotor unit is furthermore included to set the tube piece in rotation, as well as a number of feeding devices interacting with the cutting tools, e.g., ball roller screws, which have the purpose of feeding in the tools and their holder blades linearly toward the tube. The replaceable cutting inserts of the holder blades enter the envelope surface of the tube to successively cut through the tube wall and finally entirely cut off the tube. Often, four tools having a pitch of 90° are included. For several reasons, it is important that the active cutting inserts of the holder blades during operation are kept located at exactly the same radial distance from the tube. Thus, it is important that individual cutting inserts are not loaded harder than others, and that all active cutting inserts become worn essentially uniformly. In such a way, the cutting inserts obtain the same service life so that they can be replaced simultaneously.
The tool holders for previously know, open use, tools of this type include a support body for the mounting of the holder blade in the form of a plate, which in a front side includes a slot, in which the holder blade can be fixed, and on a back side includes an integrated cam having a cross-sectional V-shaped outer edge, which fits into a dovetail-shaped slot in the basic body. In the same dovetail slot, there is also housed a movable clamping wedge that interacts with two screws, which are accessible from the front side of the support body and by means of which the same can be pressed out toward the opposite outer edge of the dovetail slot and thereby wedge up the support body in a desired axial position in relation to the basic body. The holder blade in turn is fixed in a desired axial position in relation to the support body in the external slot by means of a plurality of (usually at least three) clamping jaws, which apply an uniformly distributed clamping force to an upper longitudinal edge along the blade, whereby a cross-sectional V-shaped lower longitudinal edge is pressed against an inclined, lower interface of the slot.
A disadvantage of previously known cutting tools of the kind in question is that replacement of cutting inserts and/or holder blades is intricate and time-consuming, more precisely as a consequence of the holder blade being freely movable in the appurtenant slot in the support body as soon as the securing clamping jaws have been disengaged. This means that the exact, radial distance of the different holder blades and cutting inserts from the tube to be machined has to be determined by manual measuring and fine adjustment of the axial position of the holder blade along the support body. Because the positional accuracy of the cutting inserts is in the order of 0.1 mm, it is easily realized that the operation of setting the holder blades in, for instance, four tangentially spaced-apart tools becomes difficult and time-consuming. Thus, in practice, insert replacements or work in connection with adjustment of the machine for different tube dimensions, may require 1-2 hours. This should be compared to the normal service life of the individual cutting inserts, which most often is within the range of 10-15 minutes. The set-up times of the machine between periods of operative running are accordingly disproportionately long, and entail considerable costs.
The present disclosure aims at avoiding the above-mentioned disadvantage of previously known cutting tools by providing an improved cutting tool. Therefore, a cutting tool, the holder blade of which can be dismounted and remounted without the need of repeated line ups and fine adjustments of its axial position is provided. An additional object is to make the exact positioning of the cutting inserts more effective in relation to the centre of the machine in connection with the occasions when the dimensions of the tube or work piece require adjustment of the tool, or when other cutting inserts and/or holder blades need to be mounted in the tool.
Accordingly, a set-up body is arranged between the basic body and the support body. The set-up body is actuated by a spring device aiming to displace the set-up body axially in relation to the basic body, and against the action of which the set-up body is fixable in a desired position in relation to the basic body by means of a screw joint, besides which the holder blade is fixed in a predetermined position in the slot of the support body by means of a stop member including a screw that extends so through a through hole in the holder blade and is tightened in a threaded hole that mouths in a bottom of the slot.
In one embodiment, the width of the slot between the border edges thereof is greater than the width of the holder blade between the two longitudinal edges, so as to allow mounting and dismounting of the holder blade with a side surface facing the bottom of the slot. In addition, the through hole in the holder blade has a keyhole-like contour shape by including on one hand a circular section, the diameter of which is greater than the diameter of a head of the screw, and on the other hand an elongate section that extends from the round section to an end surface and has a width that is smaller than the diameter of the screw head. In such a way, dismounting of the holder blade is allowed by the simple measure of loosening the screw a turn or so and displacing the blade in such a way that the round section of the hole ends up in line with the screw head, wherein the last-mentioned one can pass through the hole when the blade is brought out of the slot. In a reverse way, the holder blade can be remounted in the slot in order to, after tightening of the screw, recapture its exact radial position in relation to the center of the machine.
In yet another embodiment, the holder blade includes seats and cutting inserts at the two ends thereof. The key hole includes two diametrically opposed, elongate sections running from a common, circular section. The end surfaces of the elongate sections are situated at one and the same axial distance from an adjacent seat and cutting insert, respectively. In such a way, changing of the two cutting inserts can be carried out quickly and easily without the exact positioning thereof in relation to the machine center being lost.
In still another embodiment, the holder blade includes seats and cutting inserts at the two ends thereof, the blade having two separate through holes having a keyhole-like contour, each keyhole-like contour including a single elongate section running from a circular section, the end surfaces of each elongate section being situated at the same axial distance from an adjacent seat and cutting insert, respectively. Also in this embodiment, changing of the two cutting inserts can be carried out quickly and easily without the exact positioning thereof in relation to the no machine center being lost. In addition, the end surface of each elongated section can be placed closer to the free end of the blade without weakening the blade.
In another embodiment, the set-up body of the tool holder comprises means for detachably receiving a projecting sensor having the purpose of determining the position of the detached and spring-loaded set-up body in relation to the basic body depending on the distance to a work piece. Because the sensor is detachably connected with the set-up body, the same can be quickly and easily removed from the set-up body after completion of task, in order not to interfere with the machining operation.
The present embodiments eliminate the need to line up and finely adjust the holder blade in relation to the appurtenant support body and instead moving the requisite setting function to a set-up body that is arranged between the support body and the basic body and in relation to which the support body assumes a fixed axial position as soon as the setting operation has been carried out.